A missing terror suspect who fled in a burka has won a significant Court of Appeal battle over the use of secret evidence in anti-terrorism cases.

Mohammed Ahmed Mohamed, 27, who gained his legal victory with the assistance of legal aid, is said to have received al Qaida-linked terrorist training in 2008.

His whereabouts are currently unknown after he left a mosque in Acton, west London, disguised as a woman in a burka last November.

Three Court of Appeal judges allowed his appeal and that of another terrorist suspect, referred to as "CF", against an Administrative Court decision upholding the Home Secretary's decision to impose anti-terror restrictions on the basis of secret evidence.

In a ruling with important implications for future terrorism-linked cases, the judges unanimously ruled the men should have been told at least the "gist" of the allegations against them and said their cases must be reconsidered.

In particular the ruling raises questions over the "neither confirm nor deny" policy which the Government employs when allegations are made touching on national security issues.

If, when their cases are reconsidered, they they win their legal argument, Mohamed and CF could be entitled to claim damages for human rights breaches relating to the anti-terror laws.

A Home Office spokeswoman said: "We are disappointed by the Court of Appeal ruling. We are considering whether to appeal (to the Supreme Court)."

Mohamed and CF, both British citizens of Somali origin, travelled to Somaliland in east Africa and were arrested and detained there in January 2011.

They alleged they were tortured and then returned to the UK the following March with the "collusion" of the British authorities.

Both challenged the legality of control orders made for public protection under the Prevention of Terrorism Act 2005 and subsequent notices under the Terrorism Prevention and Investigation Act - the Tpim Act.

They asked Administrative Court judge Lord Justice Lloyd Jones to rule the orders had been unlawfully obtained as a result of the collusion and were an abuse of power.

The judge rejected their case and ruled in 2012 that there were reasonable grounds for the Home Secretary to believe that the men had been involved in terrorism-related activity, including plans to target western interests in Somaliland.

But the judge said he could not set out in his "open" judgment - a version of his ruling for public consumption - evidence against the men relied on by Home Secretary Theresa May, also kept secret from the men themselves.

The Home Secretary's lawyers said in open court she could "neither confirm nor deny" that the UK authorities were involved in the men's arrest in Somaliland.

Lord Justice Lloyd Jones said he had addressed the collusion issues "in detail in my closed judgment" - a version kept secret for reasons of national security.

Lord Maurice Kay ruled the terrorism suspects were entitled under human rights laws to know the "gist" of the Home Secretary's case on collusion and mistreatment.

James Eadie QC, appearing for the Home Secretary, had argued both men posed serious national security risks and their interests were adequately protected by the court processes involved in the private hearings that led to the closed judgment.

Rejecting Mr Eadie's arguments, Lord Justice Kay said: "It is no answer that terrorism is horrendous and that the unappealed factual findings against those appellants are of considerable gravity."

The judge observed: "L urking just below the surface of a case such as this is the governmental policy of 'neither confirm nor deny' (NCND).

"I do not doubt that there are circumstances in which the courts should respect it. However, it is not a legal principle."

It was a "departure from procedural norms" and required justification, said the judge.

"It is not simply a matter of a governmental party to litigation hoisting the NCND flag and the court automatically saluting it.

"Where statute does not delineate the boundaries of open justice, it is for the court to do so.

"In the present case I do not consider that the appellants or the public should be denied all knowledge of the extent to which their factual and/or legal case on collusion and mistreatment was accepted or rejected.

"Such a total denial offends justice and propriety. It is for these fundamental reasons that I consider the appellants' principal ground of appeal is made out.

"The approach to their abuse of process applications was largely flawed. I make no comment on the merits of those applications."

The judge said the appropriate course was to remit the case back to the Administrative Court "so that the whole issue of abuse of process can be reconsidered in the light of this judgment".

The court had heard how the security services became aware in 2010 that Mohamed was planning a Somaliland trip in December that year and obtained a control order restricting his movements.

But he did not travel until January 2011. On January 13, the Home Secretary was given permission by Mr Justice Silber to make a fresh control order.

The following day Mohamed was arrested and detained until March 13 2011, when both men were deported back to the UK.

CF was prosecuted for allegedly attempting to travel to Afghanistan to engage in acts of terrorism but was acquitted in 2009, but by that time had absconded to Somalia.

When he returned to the UK in 2011 he was imprisoned for breaching his bail conditions two years earlier and not released until May 11 2011 when anti-terror restrictions were imposed.

Lord Justice Maurice Kay said the appeal court had wondered whether Mohamed's appeal against the Administrative Court decision should be stayed after he absconded in a burka last year.

But although his legal aid was initially withdrawn, it was reinstated, and the Home Secretary decided not ask the court to dismiss his appeal as CF's case was going ahead in any event.

Lord Justice Kay said: "With some reluctance, we allowed it to proceed."

He warned the fact that the appeal court had dealt with Mohamed's appeal "notwithstanding his unknown whereabouts" did not necessarily mean that the Administrative Court would do so - "nor does our decision seek to influence future consideration of his public funding".

But the control orders made against the men that had now expired would be quashed because there had been a "material non-disclosure" of information when the Home Secretary went to court to obtain permission to make them.

The Tpim imposed on Mohamed was due to expire later this month, while the similar order on CF expired on January 2.

Legal aid was withdrawn from him just before Christmas, but reinstated following an appeal to an adjudicator.

It is thought Mohamed used a sharp instrument to cut off his tag and was last seen at the An-Noor Masjid and Community Centre in west London.

He was due to stand trial on April 28 on charges of breaking the Tpim restrictions but the trial date was "vacated" following a request from the prosecution.

Both Mohamed and CF say British "officers and agents ... by their acts and omissions procured, induced, encouraged or directly caused, or were otherwise complicit in" their detention, assault and mistreatment and torture while held by the Somaliland authorities.